ASTM D6139 Standard Test Method for Determining the Aerobic Aquatic Biodegradation of Lubricants or Their Components Using the Gledhill Shake Flask

Get Certified ASTM D6139 Testing for Reliable Lubricant Biodegradation Data

Any lubricant intentionally or unintentionally released into rivers, lakes or coastal waters can last in the environment if it is resistant to biodegradation, and manufacturers and regulators now ask for biodegradation data before a product can feature an environmentally acceptable lubricant claim. When there is limited water solubility or multi-component formulations, the formulators can use the shake flask procedure outlined in ASTM D6139. ASTM D6139 data are used to support environmental claims, formulation comparisons, and assessment of base oils and additives for new formulations by analysts and product-development teams.

• Establishes the degree of aerobic aquatic biodegradation for fully formulated lubricants or their individual components.
• Measures ultimate biodegradation by carbon dioxide (CO₂) evolution rather than an indirect indicator.
• Tackles the challenge of testing water-insoluble materials and complex mixtures, which many ready-biodegradability tests are not designed to handle.
• Applies to all non-volatile lubricants or components that are not toxic or inhibitory to the inoculum organisms at the test concentration.
• Reports all results in SI units as the only unit system specified by the standard.

What are the Uses of ASTM D6139 Testing? 

ASTM D6139 testing enables formulators and environmental scientists to generate biodegradation data for lubricants resistant to evaluation by other test methods. This standard-

• Establishes whether a lubricant or lubricant component biodegrades enough to support an environmentally acceptable lubricant claim.
• Supports formulators in comparing the biodegradability of different base oils, additives, or fully formulated products.
• Supports manufacturers in generating data for ecolabel programs and environmental regulatory submissions.
• Determines the validity of a test run based on the biodegradation of a reference material.
• Supports analysts in choosing an inoculum source such as activated sewage sludge, soil, or natural surface water that best represents the intended field application.

Which materials can be tested under ASTM D6139? 

ASTM D6139 covers fully formulated lubricants and their individual components, provided that the material is non-volatile and not toxic or inhibitory to the inoculum organisms at the test concentration. The method suits materials with limited water solubility, since the Gledhill shake flask targets the complex, largely water-insoluble mixtures typical of many lubricants. An analyst determines the carbon content of the test substance before testing to calculate the theoretical CO₂ yield and select an appropriate inoculum source based on the material’s intended application.

Why is ASTM D6139 Important? 

ASTM D 6139 gives the lubricant industry a test method designed specifically to target those characteristics that make lubricants challenging to assess for aquatic biodegradation under standard test conditions. Thus, analysts may expect a lubricant that demonstrates a good degree of biodegradation under the ASTM D 6139 test protocol to biodegrade in most aerobic aquatic environments. Low CO₂ production does not necessarily indicate resistance to biodegradation; rather, it suggests the analyst should perform additional tests or provide more information on the test material’s possible inhibitory effect on the inoculum. Before an analyst judges the test material’s biodegradability, ASTM D6139 confirms the inoculum’s viability and capacity to yield meaningful results by requiring confirmation with a reference material during each test.

ASTM D5997 Testing Process and Data Collection 

An engineer identifies the water stream that requires continuous carbon monitoring and selects a corresponding analyzer. Technicians install the sample line, acidification stage, and membrane conductivity module into the process and system and calibrate the analyzer. The analyzer then automatically oxidizes organic carbon in the water stream, passes the CO₂ through a selective membrane, and measures the resulting change in conductivity. Analysts then evaluate the resulting trend of total carbon, inorganic carbon, and total organic carbon in relation to the process water limit.

Common Challenges and Troubleshooting

Stable sample flow, working membrane modules, and standardized reagents are required to obtain accurate results by employing the ASTM D5997 method. Baseline changes in the conductivity detector may occur due to fouling or drift. The acidification and oxidation stages are periodically monitored, and calibration is compared to reference materials to ensure that the analyzer remains within its limits of 0.5 µg/L to 50,000 µg/L.

• The analyst enters and reports values of total carbon, inorganic carbon, and total organic carbon in micrograms per liter (μg/L), the unit the standard specifies for all results.
• The report identifies whether the water source falls into a low-carbon category (such as semiconductor or power-plant feedwater with TOC below 1 μg/L) or a higher-tolerance category (such as pharmaceutical cleaning water between 500 μg/L and 50,000 μg/L).
• The report accounts for temperature effects on the conductivity measurement through the chemometric model built into the analyzer.
• The report tracks carbon levels as a continuous trend rather than a single pass/fail value, so engineers can identify a shift before it exceeds a specification limit.

Link to ASTM D6139